import java.util.*;

public class Hirschberg
{
   static int K[][];

   /* ==================================================================
      findLCS(m, n, A, B): find the LCS in A[0..(m-1)] and B[0..(n-1)]
      ================================================================== */
   public static String findLCS(int m, int n, String A, String B)
   {
      int i, j;
      String C = "";

      if ( A.length() != m || B.length() != n )
      {
	 System.out.println("Problem !");
      }

      if ( n == 0 )
         return "";

      if ( m == 1 )
      {
         /* =====================================
	    The input A consists of 1 character
	    Find the single common character in B
            ===================================== */
         for ( i = 0; i < n; i++ )
	    if ( B.charAt(i) == A.charAt(0) )
	       return( A );

	 return "";	// Not found....
      }

      /* =====================================================
	 General case:  A[0..(m-1)] has 2 or more characters
         ===================================================== */

      i = m/2 ;
      int x1=0, x2=0;
      int z = solveLCS( A, B ) ;
/*
      System.out.println("LCS( " + A + "," + B + ") = " + z );
*/
      for ( j = 0; j < n; j++ )
      {
          x1 = solveLCS( A.substring(0, i), B.substring(0, j) ) ;
          x2 = solveLCS( A.substring(i, m), B.substring(j, n) ) ;
/*
          System.out.println("Trying: ");
          System.out.println(" " + A.substring(0, i) 
			+ "<->" + B.substring(0, j) + " ==> " + x1);
          System.out.println(" " + A.substring(i, m) 
			+ "<->" + B.substring(j, n) + " ==> " + x2);
*/
	  if ( x1 + x2 == z )
	     break;
      }

      if ( x1 + x2 != z )
      {
	 System.out.println("x1 + x2 == z NOT FOUND !");
      }

      String C1 = findLCS(i, j, A.substring(0,i), B.substring(0,j) );
      String C2 = findLCS(m-i, n-j, A.substring(i,m), B.substring(j,n) );

      System.out.println("C1 = " + C1 + ", C2 = " + C2);

      return ( C1 + C2 );
   }


   public static int solveLCS(String x, String y)
   {
      int i, j;

      if ( x.length() == 0 || y.length() == 0 )
	 return 0;

      for (j = 0; j < y.length()+1; j++)
         K[1][j] = 0;        // x = "" ===> LCS = 0


      for (i = 1; i < x.length()+1; i++) 
      {
         /* =====================================================
            Recycle phase: copy row K[1][...] to row K[0][...]
	    ===================================================== */
         for ( j = 0; j < y.length()+1; j++)
	    K[0][j] = K[1][j];


         K[1][0] = 0;        // y = "" ===> LCS = 0     

         for (j = 1; j < y.length()+1; j++)
	 {
            if ( x.charAt(i-1) == y.charAt(j-1) )
            {
               K[1][j] = K[0][j-1] + 1;
            }
            else
            {
               K[1][j] = Math.max( K[0][j], K[1][j-1] );
            }
         }
      }

      return K[1][y.length()];
   }





   public static void main(String[] args)
   {

       Scanner in = new Scanner(System.in);

       String x;
       String y;
       String z;
       int i, j, r;


       System.out.print("x = ");
       x = in.next();
       System.out.print("y = ");
       y = in.next();

       K = new int[2][y.length()+1];    // Linear space !!!

       z = findLCS(x.length(), y.length(), x, y);

       System.out.println("LCS = " + z);
   }

}